Motivation behind the development of this project
Presently, over 1 million people, in the U.S. alone, are insulin dependent diabetics and about 40 thousand additional people are diagnosed each year.
Each year there is over $14 billion dollars spent on treating insulin dependent diabetes and lost wages due to it.
While technology has greatly improved treatment and management of insulin dependent diabetes, the costs seem to increase geometrically (especially to those without insurance).
The cornerstone to managing insulin dependent diabetes is monitoring blood glucose levels. Presently, the only methods available for monitoring blood glucose rely on single use, disposable, test strips or longer term Continuous Blood Glucose Monitors. While CGM's provide a fantastic method of tracking and, as a result, controlling blood glucose levels, they do so at a very high monetary cost since they require special sensors that need to be replaced every 10-14 days. In addition, CGM's need calibration through the use of test strips. Despite all the technological advances in medicine we continue to rely on the same methods of measuring blood glucose as 40-50 years ago (enzymatic... not really much different than the first Glucometer that I used in the mid 1980's).
Since I first researched this idea, last year, there have been numerous research projects published in respected journals that have, independently, followed similar ideas and direction. They all seem to achieve the objective of measuring ketone levels. Despite this, no products have been produced.
Theory behind this project:
Our bodies produce ketones (through the breakdown of fatty acids in the liver) when glucose is unavailable to the bodies cells. This occurs, either under fasting conditions (essentially low intake of carbohydrates) or when there is insufficient insulin present to transport glucose into the tissues of our bodies.
The breakdown of fatty acids produces the ketone bodies - aceto-acetate and beta-hydroxybutyrate, both of which are acidic and lower blood pH, when they reach high levels. To maintain blood pH levels acetoacetate is excreted through the kidney's and also the lungs (as acetone - resulting in the fruity odor on the breath of those in ketosis). Diabetic Keto-Acidosis is most likely to occur when individuals are sick, stressed, have blood glucose over 300 or in women, who are pregnant, with any type of diabetes.
In those of us who are not insulin dependent diabetics it is normal to produce Ketones when blood glucose levels begin to drop. For those with insulin dependent diabetes, the production of Ketones begins when there is insufficient insulin present to transport glucose into cells (regardless of how much glucose is present).
For insulin dependent diabetics, when there is plenty of glucose available but no insulin then Ketoacidosis can develop. Diabetic Keto-Acidosis is the most common cause of death for young people diagnosed with insulin dependent diabetes.
This makes analysis of ketone levels useful for treatment of insulin dependent diabetes.
The main ketone bodies produced by our bodies are:
- Beta-hydroxybutyrate – used in blood tests for ketones
- Acetoacetate – used in urine tests for ketones
- Acetone – target for breath tests for ketones (produced from breakdown of acetoacetate)
BetaHydroxyButyrate and Acetoacetate transported in the blood. Acetoacetate breaks down into acetone in the lungs and is excreted in exhaled breath – where it can be measured.
Exhaled breath contains numerous components (400+ ?). These components come, primarily, from the air we breath and waste produced from metabolism within our bodies. The largest proportions present in our exhaled air are: … CO2, H2O,
During Exhaltion – first portion of breath is from our mouth and trachea, the next portion of breath is from our bronchi and bronchioli, the final of breath comes from our avioli.
The target portion of exhaled breath that we are most interested in is the aviolar portion, that is where gas exchange takes place and where the highest proportion of acetone will be present.
Challenges this project faces:
sensitivity and specificity
increase both by minimizing interfering factors and targeting end of exhalation for measurement
- sensor sensitive enough to the presence of acetone (within levels that we need to detect)
- sensor specific enough to acetone (other VOC's not mistaken for acetone, such as ethanol)
- minimize interfering factors (humidity especially – need desiccant)
- ensure a slow and full exhalation (timed exhale) – to target aviolar air
This project strives to use "off the shelf" parts, with the objective of making it easy for others to reproduce.
Developing a reproducible method of calibration for Ceramic Metal Oxide gas sensors will make it easier for other hardware developers to accurately use these types of sensors - while it is easy to adjust the sensitivity of these sensors there is currently no method (that I've found) for calibrating readings with actual concentrations of the target gas (at least without purchasing known bottles of gas at known concentrations – though, I have not found acetone, but only other VOC's).
Open Source License - GNU General Public License (v3)
Open Hardware License - all schematics, gerbers, etc. will be open (once these are done I will submit them to www.oshwa.org)